US3755696A
Expired / Lapsed
US
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Detector having a constant false alarm rate and method for providing same
Assignee: Unisys Corp
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Filing: 1971-10-14
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Granted: 1973-08-28
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Expires: 1991-10-14
Abstract
Abstract A detector which may be subject to temperature variations and power supply drift comprised of an avalanche transistor circuit having a variable threshold that is sensitive to input signals within a useful frequency band and noise which produces threshold signals when the amplitude of the input signals or the noise exceeds the instantaneous value of the variable threshold. The rate at which the threshold signals are produced is determined in an N bit storage device coupled to the avalanche transistor circuit and clocked at a specific repetition rate. The storage device has each stage coupled in parallel to an AND gate and to a summation network. The AND gate produces an output signal which indicates input signals are present when each stage of the storage device applies a specified output signal to the AND gate. The summation network produces a variable output signal having an amplitude that varies at a rate proportional to the rate at which the threshold signals are produced. The variable amplitude signal is applied to a serial circuit which shunts the collector current of the avalanche transistor circuit at a rate commensurate with the rate the variable amplitude signal varies in response to noise but at a substantially lower rate than the rate the variable amplitude signal varies in response to input signals. The serial circuit thereby controls the threshold sensitivity of the avalanche transistor to provide a constant false alarm rate for the apparatus while also compensating for temperature variations and drift in the voltage level of the power supply.
Inventors
- 👤 R Brophy
- 👤 A Nicolson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 02:27
CPC Classifications
H; H03; H03K; H03K3/00; H03K3/01; H03K3/013; H03L; H03L1/00
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
264 words
A detector apparatus which may be subject to temperature variations and includes a power supply source which may be subject to drift for use with a signal source which provides input signals at known repetition rates within a useful frequency band to said detector in an environment where noise is present comprising, variable threshold means coupled to said power supply source and responsive to said input signals and said noise for providing threshold output signals when said input signals or said noise exceed the instantaneous value of said variable threshold, means coupled to said poWer supply source and to said variable threshold means for producing a variable amplitude output signal which changes amplitude at a rate proportional to the rate at which said threshold output signals are provided, preset threshold means coupled to said power supply source and to said means for producing a variable amplitude output signal which produces an indicator output signal when a pre-determined number of said threshold output signals have been provided, and shunt means coupled between said means for producing a variable amplitude output signal and said variable threshold means for controlling said instantaneous value of said variable threshold in response to said variable amplitude output signal whereby said variable threshold means provides threshold output signals in response to said noise at a constant first rate that is substantially different from a second rate at which said threshold output signals are produced in response to said input signals and said first rate is maintained constant thereby in the presence of temperature variations and drift in said power supply source.
Claim 2
Dependent Claim
264 words
A detector apparatus which may be subject to temperature variations and includes a power supply source which may be subject to drift for use with a signal source which provides input signals at known repetition rates within a useful frequency band to said detector in an environment where noise is present comprising, variable threshold means coupled to said power supply source and responsive to said input signals and said noise for providing threshold output signals when said input signals or said noise exceed the instantaneous value of said variable threshold, means coupled to said poWer supply source and to said variable threshold means for producing a variable amplitude output signal which changes amplitude at a rate proportional to the rate at which said threshold output signals are provided, preset threshold means coupled to said power supply source and to said means for producing a variable amplitude output signal which produces an indicator output signal when a pre-determined number of said threshold output signals have been provided, and shunt means coupled between said means for producing a variable amplitude output signal and said variable threshold means for controlling said instantaneous value of said variable threshold in response to said variable amplitude output signal whereby said variable threshold means provides threshold output signals in response to said noise at a constant first rate that is substantially different from a second rate at which said threshold output signals are produced in response to said input signals and said first rate is maintained constant thereby in the presence of temperature variations and drift in said power supply source.
Claim 3
Dependent Claim
40 words
A detector apparatus as described in claim 1 in which said variable threshold means includes means in which said variable threshold is varied by controlling the amount of current drawn from said power supply source through said variable threshold means.
Claim 4
Dependent Claim
23 words
A detector apparatus as described in claim 1 in which said variable threshold means includes an avalanche transistor operating in its zener mode.
Claim 5
Dependent Claim
40 words
A detector apparatus as described in claim 1 in which said detector further includes gating means coupled to said variable threshold means for applying gating signals to said variable threshold means which alter the sensitivity of said variable threshold means.
Claim 6
Dependent Claim
33 words
A detector apparatus as described in claim 4 in which said gating means includes means for altering the sensitivity of said variable threshold means at a periodic rate for specific increments of time.
Claim 7
Dependent Claim
43 words
A detector apparatus as described in claim 1 which further includes means coupled between said variable threshold means and said means for producing a variable amplitude output signal which increases the duration of said threshold output signals provided by said variable threshold means.
Claim 8
Dependent Claim
35 words
A detector apparatus as described in claim 1 in which said means for producing a variable amplitude output signal includes means for storing a plurality of threshold output signals for a specific period of time.
Claim 9
Dependent Claim
36 words
A detector apparatus as described in claim 7 in which said means for producing a variable amplitude output signal further includes means for summing said plurality of threshold output signals stored in said means for storing.
Claim 10
Dependent Claim
45 words
A detector apparatus as described in claim 8 in which said means for summing produces a variable amplitude output signal which varies at a rate determined by the number of threshold output signals coupled into said means for storing for a specific period of time.
Claim 11
Dependent Claim
20 words
A detector apparatus as described in claim 7 in which said means for storing includes an analog gated dumped integrator.
Claim 12
Dependent Claim
38 words
A detector apparatus as described in claim 7 in which said shunt means includes means for establishing an average number of threshold outputs that will be produced by said variable threshold means over said specific period of time.
Claim 13
Dependent Claim
64 words
A detector apparatus as described in claim 11 in which said means for establishing said average number of threshold outputs over said period of time includes a transistor circuit having an emitter resistor with a resistance value which may be selected to determine said average number of threshold output signals that will be stored in said storage means over said specific period of time.
Claim 14
Dependent Claim
35 words
A detector apparatus as described in claim 1 in which said variable threshold means for producing a variable amplitude output signal includes a series circuit comprising a shift register storage device and a summation circuit.
Claim 15
Dependent Claim
20 words
A detector apparatus as described In claim 13 in which said storage device includes a serial-in parallel-out N-bit shift register.
Claim 16
Dependent Claim
26 words
A detector apparatus as described in claim 13 in which said storage device includes a serial-in serial-out N-bit shift register and a log2N stage up/down counter.
Claim 17
Dependent Claim
38 words
A detector apparatus as described in claim 1 in which said preset threshold means includes means for producing an indicator output signal when said means for producing a variable amplitude output signal produces a maximum amplitude output signal.
Claim 18
Dependent Claim
48 words
A detector apparatus as described in claim 1 in which said preset threshold means includes logic circuit means for providing an indicator output signal when said means for producing a variable amplitude output signal produces an output signal which is a specified fraction of a maximum output signal.
Claim 19
Dependent Claim
56 words
A detector apparatus as described in claim 1 in which said shunt means includes means which shunts a minimum amount of current from said variable threshold means when said number of said threshold output signals are a minimum and shunts a maximum amount of current when said number of said threshold output signals are a maximum.
Claim 20
Dependent Claim
30 words
A detector apparatus as described in claim 18 in which said shunt means further includes means for controlling the rate at which said current through said shunt means is varied.
Claim 21
Dependent Claim
68 words
A detector apparatus as described in claim 19 in which said means for controlling the rate at which said current through said shunt means is varied permits said current to vary at a slow rate when said variable amplitude output signal changes at a slow rate but inhibits said current from varying at a fast rate when said variable amplitude output signal changes amplitude at a fast rate.
Claim 22
Dependent Claim
31 words
A detector apparatus as described in claim 1 in which said shunt means includes a series circuit comprising a low pass filter having a specific time constant and a transistor circuit.
Claim 23
Independent Claim
199 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals within a useful frequency band in an environment where noise is present comprising the steps of, sensing input signals in a variable threshold means that are in excess of an instantaneous value of said variable threshold, sensing noise in said variable threshold means that is in excess of said instantaneous value of said variable threshold, producing detected output signals in response to said sensed input signals, producing detected output signals in response to said noise, producing a variable amplitude output signal proportional to the rate at which said detected output signals are produced, sensing in a preset threshold device when a plurality of said detected output signals are produced in excess of said preset threshold, producing an indicator output signal when said detected output signals exceed said preset threshold, and controlling said instantaneous value of said variable threshold in said variable threshold means with said variable amplitude output signals whereby said detected output signals produced in response to said noise are produced at a constant rate that is less than the rate said detected output signals produced in response to said input signals.
Claim 24
Independent Claim
199 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals within a useful frequency band in an environment where noise is present comprising the steps of, sensing input signals in a variable threshold means that are in excess of an instantaneous value of said variable threshold, sensing noise in said variable threshold means that is in excess of said instantaneous value of said variable threshold, producing detected output signals in response to said sensed input signals, producing detected output signals in response to said noise, producing a variable amplitude output signal proportional to the rate at which said detected output signals are produced, sensing in a preset threshold device when a plurality of said detected output signals are produced in excess of said preset threshold, producing an indicator output signal when said detected output signals exceed said preset threshold, and controlling said instantaneous value of said variable threshold in said variable threshold means with said variable amplitude output signals whereby said detected output signals produced in response to said noise are produced at a constant rate that is less than the rate said detected output signals produced in response to said input signals.
Claim 25
Dependent Claim
68 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals as described in claim 22 which further includes the steps of, gating said variable threshold means at specified repetition rates for a pre-determined period of time thereby increasing the sensitivity of said threshold means for said periods of time, and storing said detected output signals for a fixed number of repetition rates.
Claim 26
Dependent Claim
91 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals as described in claim 22 which further includes the steps of, varying said instantaneous value of said variable threshold at a rate commensurate with said rate at which said detected output signals are produced iN response to said noise, and varying said instantaneous value of said variable threshold in said variable threshold means at a rate that is substantially less than the rate said detected output signals are produced in response to said input signals.
Claim 27
Independent Claim
284 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals within a useful frequency band in an environment where noise is present comprising the steps of, applying input signals of sufficient magnitude to the base terminal of an avalanche transistor operating in the zener mode to cause reverse breakdown in said avalanche transistor, applying noise of sufficient magnitude to said base terminal of said avalanche transistor to produce reverse breakdown, producing avalanche transistor output signals in response to said applied input signals, producing output signals in response to said noise, increasing the pulse width of said output signals produced by said avalanche transistor, storing a plurality of said pulses as digital 1s in a counter, sensing in a preset threshold device when a plurality of said stored digital 1s are in excess of said preset threshold, producing an indicator output signal when said stored digital 1s exceed said preset threshold, producing a variable amplitude analog output voltage proportional to the rate at which said avalanche transistor detector produces output signals, applying said analog output voltage to the base terminal of a shunt transistor circuit to control the amount of current drawn through said transistor, and controlling the rate at which the current is drawn through said transistor circuit thereby current is varied at a rate which is commensurate with the rate of change in said amplitude of said analog output voltage when said voltage is produced in response to said noise but the rate at which said current is varied is substantially less than the rate at which said amplitude of said analog output voltage is changed in response to detector output signals produced by said input signals.
Claim 28
Independent Claim
284 words
A method for providing a constant false alarm rate in an apparatus for detecting input signals within a useful frequency band in an environment where noise is present comprising the steps of, applying input signals of sufficient magnitude to the base terminal of an avalanche transistor operating in the zener mode to cause reverse breakdown in said avalanche transistor, applying noise of sufficient magnitude to said base terminal of said avalanche transistor to produce reverse breakdown, producing avalanche transistor output signals in response to said applied input signals, producing output signals in response to said noise, increasing the pulse width of said output signals produced by said avalanche transistor, storing a plurality of said pulses as digital 1s in a counter, sensing in a preset threshold device when a plurality of said stored digital 1s are in excess of said preset threshold, producing an indicator output signal when said stored digital 1s exceed said preset threshold, producing a variable amplitude analog output voltage proportional to the rate at which said avalanche transistor detector produces output signals, applying said analog output voltage to the base terminal of a shunt transistor circuit to control the amount of current drawn through said transistor, and controlling the rate at which the current is drawn through said transistor circuit thereby current is varied at a rate which is commensurate with the rate of change in said amplitude of said analog output voltage when said voltage is produced in response to said noise but the rate at which said current is varied is substantially less than the rate at which said amplitude of said analog output voltage is changed in response to detector output signals produced by said input signals.
References Cited (Backward Citations)
US3280340A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |